Refrigerant vapor compression systems are well known in the art and commonly used for conditioning air to be supplied to a climate controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility. Refrigerant vapor compression systems are also commonly used in refrigerating air supplied to display cases, merchandisers, freezer cabinets, cold rooms or other perishable/frozen product storage area in commercial establishments. Refrigerant vapor compression systems are also commonly used in transport refrigeration systems for refrigerating air supplied to a temperature controlled cargo space of a truck, trailer, container or the like for transporting perishable/frozen items by truck, rail, ship or intermodally.
Such refrigerant vapor compression systems include a compression device, a condenser heat exchanger, an evaporator expansion device, such as for example an electronic expansion valve or a thermostatic expansion valve, and an evaporator heat exchanger, arranged in series refrigerant flow relationship in a refrigerant flow circuit according to a refrigeration cycle. Many refrigerant vapor compression systems also include a receiver interdisposed in the refrigerant circuit, generally downstream with respect to refrigerant flow of the condenser and upstream with respect to refrigerant flow of the evaporator expansion device. The receiver functions to collect liquid refrigerant passing from the condenser heat exchanger and stores excess refrigerant. Conventional receivers typically include an inlet port through which refrigerant enters the receiver and a single outlet through which liquid refrigerant may pass out of the receiver. A discharge valve, for example a check valve, is typically mounted to the single receiver outlet to control refrigerant flow discharging from the receiver back into the refrigerant circuit upstream of the evaporator expansion valve. Additionally, many refrigerant vapor compression systems include a refrigerant filter-dryer interdisposed in the refrigerant flow circuit downstream with respect to refrigerant flow of the receiver and upstream with respect to refrigerant flow of the evaporator expansion valve. The filter-dryer functions to remove foreign matter and moisture from the refrigerant flowing therethrough. U.S. Pat. No. 7,571,622 combined in-line accumulator/filter dryer unit disposed between the two heat exchangers of a reversible refrigeration system.
In some refrigeration cycles, the refrigerant vapor compression system further includes a liquid injection line establishing refrigerant flow communication between the receiver and the suction side of the compression device. When a liquid injection line is present, a portion of the liquid refrigerant discharging from the single outlet of the receiver via the discharge valve passes through the liquid injection line to reenter the refrigerant flow circuit downstream with respect to refrigerant flow of the evaporator heat exchanger and upstream with respect to refrigerant flow of the suction inlet of the compression device, thereby bypassing the evaporator heat exchanger. A flow metering valve is disposed in the liquid injection line so that a controller can selectively meter the flow of liquid refrigerant through the liquid injection line for compressor capacity control and/or compressor discharge temperature control. Conventionally, this flow metering valve is an electronic expansion valve having a selectively variable flow area or a solenoid valve having a relatively small fixed area metering orifice, that is a fixed area orifice having a port diameter less than 2.0 millimeters.